Soviet pilots in WWII had to endure incredible hardships. Often, they flew from rough fields in lousy weather against Germans flying better aircraft. However, there was one other thing that goes a long way to explaining this excerpt from the link you provided:

"While the number of American W.W.II fighter aces, who shot down 20 or more aircraft, barely exceeds two dozen, the number of Soviet aces, who shot down 29 or more aircraft is well over a hundred. The number of Soviet aces credited with shooting down 20 or more aircraft during the Second World War is in hundreds. [Soviet Aces of World War 2, Hugh Morgan, Osprey aerospace, 1998]"

Soviet pilots, like their German counterparts, had no rotation system in place. From the time they began flying combat missions, they continued until they were killed, incapacited, or the war was over. By contrast, American and British fighter pilots were rotated out of combat after flying 100 missions. Some flew more than one tour of operations but none flew as many as the top Russian and German pilots.